I've got those buttons on my dell mouse, and never used them... I think they're for changing between pages (back-forward?). Then, there's one small square one, on top with an arrow on it... when it is clicked, the "light bar" on the mouse changes from 1 bar - to two,three, or four bars... I have no clue what that does... I' m thinking maybe a "volume" control?
Anyways... some mouse buttons can be configured in the computer's control panel to do different stuff - like switching the right for the left, so maybe that might help. Or are you speaking about a joystick with a button on top? THAT would be different!